Apparatus, system and method for measuring resistance of an inhaler

ABSTRACT

An apparatus, a closed-loop system and method for measuring the resistance of inhalation systems and/or devices are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/722,464 filed Mar. 11, 2010 which claims the benefit of U.S.provisional patent application No. 61/159,415, filed Mar. 11, 2009, thedisclosures each of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates to a device, system and methods formeasuring the resistance of inhalers to air flow. In particular, theapparatus and system can be used to measure the resistance to air flowof dry powder inhalers, which are used for pulmonary drug delivery.

BACKGROUND

Dry powder inhalers such as those described in U.S. Pat. Nos. 7,305,986,7,464,706 and U.S. patent application Ser. No. 12/484,129(2009/0308391), which disclosure is incorporated herein by reference intheir entirety, can generate primary drug particles or suitableinhalation plumes during an inspiratory maneuver by deagglomerating thepowder formulation within a container, capsule, or a cartridge. Dosingreproducibility requires that the drug formulation is uniform and thatthe dose can be delivered to the patient with consistent andreproducible results. Therefore, the dosing system must operate tocompletely discharge all of the formulation effectively during aninspiratory maneuver when the patient is taking his/her dose. Thebenefits of delivering drugs via the pulmonary circulation are numerousand include, rapid absorption into the arterial circulation, avoidanceof drug degradation by liver metabolism, ease of use, i.e., lack ofdiscomfort of administration, such as discomfort encountered by otherroutes of administration such as by injection.

The consistency in drug delivery from an inhaler is due in part to theconsistency in resistance to air flow within the air passages of theinhalation device. High resistance dry powder inhalers such as thosedisclosed in U.S. Pat. Nos. 7,305,986 and 7,464,706, and U.S. patentapplication Ser. No. 12/484,129 (2009/0308391), deliver drugformulations in a consistent manner. One of the parameters used toascertain or predict if an inhaler would deliver a dose with consistencyduring use is by knowing the resistance to air flow of the device, whichcan be measured or determined after the device is manufactured.

Present systems and methods for measuring the resistance to air flowthrough an inhaler are cumbersome, involve numerous steps andcalculations and are subject to variations in ambient conditions.Therefore, the inventors have seen the need to design and manufacture asimple apparatus, system, and method for measuring the resistance toairflow of an inhaler in order to determine if the inhaler resistanceproperties would render the inhaler suitable for use. The present systemallows for a rapid method for measuring the resistance of inhalationsystems or the individual inhalers, in an integrated system using a fewsimple steps.

SUMMARY

An apparatus, a system and a method for measuring the resistance ofinhalation systems and/or devices are disclosed.

In embodiments described herein, the apparatus can comprise a pressurecontroller operably configured to a vacuum pump; a flow controller orflow regulator which is configured to connect to a positive air pressuregenerator; a first device comprising a first chamber and a second devicecomprising a second chamber; wherein the first chamber and the secondchamber define an airflow pathway which can be sealed from ambient airwhen attached to one another in use; one or more pressure sensors, aflow rate sensor and one or more microprocessors, at least onemicroprocessor configured with the pressure controller and at least onemicroprocessor configured with the flow controller. In one embodiment,the apparatus comprises a first device and a second device eachcomprising a microprocessor configured to control a respective valveconfigured in their respective chamber and each microprocessorcommunicates information to a data acquisition board of a computer. Inthis and other embodiments, the first device also comprises a sensorconfigured to measure pressure differential between the chambers, andthe second device comprises one or more sensors, for example, a laminarflow sensor configured to measure the flow rate of airflow within thechamber, and a pressure sensor configured to measure pressuredifferential across an inhaler. In one embodiment, the apparatus isconfigured so that the first device is firmly attached to a platform andthe second device is mounted on at least one track so that it is movableon the track and sealably attachable to the first device. In oneembodiment, the apparatus is configured to have an inhaler mountingadaptor.

A method for measuring the resistance to airflow of an inhaler is alsoprovided, comprising: installing an inhaler on a holder of an apparatuscomprising a vacuum pump; a flow controller or flow regulator which isconfigured to connect to a source of positive air pressure generatordevice; a first device comprising a first chamber and a second devicecomprising a second chamber; wherein the first chamber and the secondchamber define an airflow pathway in a sealed system devoid of changesin environmental air pressure, and an inhaler with an air conduit incommunication with the airflow pathway installed in the apparatus;measuring simultaneously the pressure differential across the inhalerand flow rate through the inhaler at predetermined pressures and flowrate settings in a controlled environment one or more times to generatepressure and flow rate measurements, and analyzing the pressure and flowrate measurements using an algorithm to determine the resistance valueof the inhaler.

In one embodiment, the apparatus comprises a first device having avalve, a second device having a valve, a differential pressure sensorwhich communicates a first set of signals to a first microprocessor, thefirst microprocessor configured to control a valve of the first devicewhich is integrally connected to a power source; a flow controllerconnected to the second device and comprising a laminar flow sensor anda pressure sensor which communicate a second set of signals with asecond microprocessor; the second microprocessor configured to detectand analyze signals from the second chamber; the first microprocessorand the second microprocessor configured to control opening and closingof the valve corresponding to the first chamber and the second chamber;and a third microprocessor to read output from corresponding sensorsoutput and an algorithm to analyze the measurements and calculateresistance to airflow of the inhaler. In one embodiment, themicroprocessors can generate and analyze data from the first set ofsignals and the second set of signals that can be correlated to theresistance to airflow of an inhaler device being tested.

In another embodiment, a method for measuring the resistance to airflowof an inhaler is provided, the method comprising: attaching an inhalerin its dosing configuration to a first device comprising a first chamberand a holder for said inhaler so that an air pathway from the firstchamber and through the inhaler air pathway to ambient air is formed;and said first chamber is closed to ambient air at its opposing end fromthe inhaler holder by the second chamber; simultaneously measuringpressure differential across the inhaler and flow rate through theinhaler in a controlled environment to generate pressure and flow ratemeasurements. In embodiments described herewith, the method of measuringthe resistance of an inhaler is performed in a controlled environment atall times by a closed-loop algorithm and the pressure and flow ratemeasurements from various or multiple tests at predetermined set pointsare analyzed with an algorithm to generate a resistance value for theinhaler.

In one embodiment, an apparatus, comprising: a first device comprising afirst chamber configured to mount an inhaler and having a first valve; asecond device comprising a second chamber having a second valve; whereinthe second device is movable and sealably attachable to the firstdevice; a pressure controller connected to the first device, andcomprising a pressure sensor which communicates a first set of signalsto a first microprocessor and integrally connected to a power source; aflow controller connected to the second device and comprising a flowsensor and a pressure sensor which communicate a second set of signalswith a second microprocessor configured to detect and analyze signalsfrom the second chamber; and the first microprocessor and said secondmicroprocessor configured to control opening and closing first valve andsecond valve, respectively and corresponding to the first chamber andthe second chamber.

In this and other embodiments, the apparatus can further comprise athird microprocessor to read output from corresponding sensors outputand implement an algorithm to analyze the measurements and calculateresistance values of the inhaler.

In another embodiment, the apparatus comprises a first device configuredto hold an inhaler in place and create a seal between the first chamberand the second chamber of the second device. In one embodiment, theapparatus the first set of signals and the second set of signalsgenerated by the first and second devices respectively, can generatedata that when analyzed by a microprocessor are correlated to resistanceto airflow of the device.

In another embodiment, the apparatus the apparatus in use to measureresistance to airflow of an inhaler is configured so that the firstdevice and the second device are configured as a closed loop systemdevoid of ambient air.

In yet another embodiment, a method for measuring the resistance toairflow of an inhaler is provided, comprising: attaching an inhaler to afirst device comprising a first chamber and a holder for said inhaler sothat an air pathway from the first chamber and through the inhaler airpathway is formed; attaching a second device comprising a second chamberto said first device to enclose said inhaler within the second chamber;actuating the apparatus to obtain a controlled constant pressureenvironment in the second chamber; and simultaneously measuring pressuredifferential across the inhaler and flow rate through the inhaler togenerate pressure and flow rate measurements. In this and otherembodiments, the controlled constant pressure environment is maintainedby a closed-loop algorithm of the apparatus in use, and wherein pressureand flow rate measurements from various test set points of the inhalerare analyzed with an alternate algorithm to generate a resistance valuefor the inhaler. In one embodiment, the resistance value for the inhaleris determined using measurement signals analyzed using a microprocessor.In alternate embodiments, the method for measuring resistance of thedevice measures pressure and flow rate at predetermined pressure dropsettings for the inhaler.

In an alternate embodiment, a method for determining resistance toairflow of an inhaler, comprising: determining the range of measurementsat which square root of the pressure differential versus flow rate curvefor an inhaler type is linear to yield predetermined value settings;obtaining pressure differential and flow rate measurements at variouspredetermined value settings within the linear range for a secondinhaler and determining the slope of the curve to obtain a resistancevalue for the inhaler. In this embodiment, the predetermined flow ratesettings are greater than 0.1 L/min and at least three predeterminedvalue settings are used to measure pressure differential and flow rateto determine the resistance value of the inhaler. In another embodiment,the method further comprises the step of measuring flow rate and squareroot of the pressure differential across an inhaler in an apparatuscomprising a first chamber and a second chamber; wherein said inhaler isinstalled in the second chamber.

In another embodiment, the method comprises analyzing data obtained frompressure differential and flow rate measurements to obtain a linearregression of pressure and flow from data collected at least threepredetermined value settings wherein the analysis results in acoefficient of determination greater than 0.9.

In an alternate embodiment, the apparatus can comprise a closed loopsystem comprising a single flow controller. In yet another embodiment,the apparatus can comprise a closed loop system comprising a singlepressure controller and a flow meter. In this aspect, the apparatus cancomprise a single chamber either around the inhaler or downstream fromthe inhaler. Measurements obtained from this system can be processed andanalyzed similarly as with an apparatus comprising a dual chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an isometric view of an embodiment of the apparatus formeasuring the resistance of an inhaler.

FIG. 2 depicts an isometric view of the embodiment illustrated in FIG. 1with an inhaler in a dosing position mounted in the inhaler holder ofthe apparatus.

FIG. 3 depicts a side view of the embodiment illustrated in FIG. 1,showing the movable part of the apparatus having a handle for holdingthe device for moving on a track.

FIG. 4 depicts a perspective view of the front of the apparatusillustrated in FIG. 1 prior to use.

FIG. 5 depicts the apparatus illustrated in FIG. 1 in a closed, andsealed, configuration or in use.

FIG. 6 depicts a perspective view of the apparatus illustrated in FIG. 5in cross-section through its longitudinal axis with an inhaler installedin the apparatus.

FIG. 7 depicts a side view of the embodiment in FIG. 5 illustrating thevarious component parts of the apparatus.

FIG. 8 illustrates a block diagram of the electronics associated withthe resistance measuring apparatus and system.

FIG. 9 is a graphic representation of an inhaler performance test usingan apparatus described herein compared to theoretical values. The dataare plotted as flow rate in the x-axis versus pressure differential fora MEDTONE® inhaler prototype.

FIG. 10 is a graphic representation of an inhaler performance test usingan apparatus described herein compared to theoretical values. The dataare plotted as flow rate in the x-axis versus pressure differential foran alternate inhaler design.

FIG. 11 is a graphic representation of an inhaler performance test usingan apparatus described herein compared to theoretical values. The dataare plotted as flow rate in the x-axis versus pressure differential foryet another inhaler design.

FIG. 12 depicts a graph showing the pressure differential and flow ratemeasurements from the data depicted in FIG. 9 for a MEDTONE® inhalerprototype and the calculated resistance value for the inhaler tested.

FIG. 13 also depicts a graph showing the pressure differential and flowrate measurements from the data depicted in FIG. 10 for a second inhalerprototype and the calculated resistance value for the inhaler tested.

FIG. 14 also depicts a graph showing the pressure differential and flowrate measurements from the data depicted in FIG. 11 for a third inhalerprototype and the calculated resistance value for the inhaler tested.

DETAILED DESCRIPTION

In embodiments disclosed herein, there is disclosed an apparatus, asystem, and a method for measuring the resistance of an inhalationdevice. The apparatus provides several benefits to a user since it is aclosed-loop system to control or eliminate environmental variables whichcan affect the resultant measurements and its ease of use provides arapid system for assessing and determining the performance of an inhalerdevice during manufacturing. The apparatus is integrated withmicroprocessors and uses an algorithm in a computer system whichfacilitates data manipulation, analysis, storage and/or display of themeasured parameters and calculated values in an automated manner. Theapparatus and system are easy to use and resistance value data for aninhaler can be determined quickly with more accuracy due to theelimination of variation due to daily fluctuations in atmosphericpressure, thus significantly reducing errors in calculation. In otherembodiments, the apparatus can also eliminate variables such asvariations in air temperature and relative humidity. The apparatus caneasily be configured to be adaptable to different inhaler design, can bemade of different materials, including metals or high strengthcomposites.

In one embodiment illustrated in FIGS. 1-7, the apparatus 10, comprises:a first device 11 mounted on a platform 13 by a mounting means, such asbracket 8 and comprising a first chamber 12 configured to have a holder15 to mount an inhaler 20 (FIG. 2). The first device 11 is furtherprovided with a cap 14 which has a central opening to allow a valve ortubing 16 to communicate with the interior of chamber 12. The firstdevice 11 is configured to be adapted to a pressure pump (not shown) andis configured to be adapted or fitted with a second device 17 to form acontiguous body of the apparatus 10, wherein the first device and thesecond device 17 can form a seal to ambient air. The second device 17comprises a mounting mechanism 19, such as a bracket 27 to hold thesecond chamber 18. The second device is also configured to be mounted oradapted to move on a track 21 attached to platform 13 so that the seconddevice 17 is movable on a horizontal plane to meet and engage the firstdevice 11.

In one embodiment, the first device 11 and the second device 17 areconfigured to have similar geometric shapes, such as a tubularconfiguration illustrated in FIGS. 1-7. The second device also comprisesa second chamber 18 configured to engage chamber 12 to form a tight sealand enclose the inhaler mounting area 15. As illustrated in FIGS. 1 and2, the first device comprises O-rings 23 at the end which engages thesecond device 17 to form the tight seal in excluding ambient air in use,and has an opening 9 configured to receive a tubing for communicatingwith sensors, such as pressure sensors in a pressure controller device22. Inhaler holder or inhaler adaptor 15 can be configured in any shapeor form so that any inhaler design can be adapted on the device. Inembodiments herein, adaptor 15 can be made of any material that hassealable properties and an hold the inhaler in a dosing configuration.

FIGS. 1-3 also depict the apparatus comprises a flow controller device24 connected to the second device 17 by a mounting gear 26 configuredwith a conduit 28 to allow a tubing to be adapted to supply air flow orpositive air pressure into the inside of chamber 18. The second chamber18 is configured to have an opening 25 to allow the chamber 18 tocommunicate with a pressure sensor of the pressure controller 22 inmeasuring pressure differential between or across the two chambers 12,18 in use. FIG. 3 depicts a side view of the second device 17 comprisinga handle 29 which is configured for holding the device while moving ontrack 21. Handle 29 is configured to allow manual movement of the seconddevice 17 on track 21. FIG. 3 also depicts that apparatus 10 can beprovided with adjustable feet 30 attached to platform 13 so that theapparatus can be balanced in a horizontal plane; and wherein the feetcan be provided with a shock absorbing system to prevent vibration ofthe instrument during use.

FIG. 4 depicts a front, isometric view of the apparatus showing theposition of handle 29 on mounting gear 19 of second device 17. FIGS. 5-7depict the apparatus in an in use configuration wherein first device 11and second device 17 are engaged and second device 17 is prevented frommoving by a stopping mechanism, for example, a block 31 at the end ofthe track 21 proximal to first device 11. A second stop block 32 at thedistal end of track 21 can also be provided to prevent second device 17from falling off track 21. FIG. 6 depicts a cross-section of theembodiment described in FIGS. 1-5 through its mid-longitudinal axis ofthe apparatus showing a MEDTONE® inhaler mounted on the first device andenclosed within second chamber 17.

FIG. 7 depicts a schematic representation of the components parts of theapparatus which facilitate the measurement of the resistance of aninhaler device and FIG. 8 illustrates an electronic block diagram of anembodiment of the closed-loop resistance test system described herewith.FIGS. 7 and 8 also shows the apparatus comprises a pressure controller22 comprising a valve, a microprocessor, which integrates and analyzessignals from one or more sensors, for example, pressure sensors whichdetect signals in chambers 12, 18, for example, pressure differentialacross the chambers to the data acquisition board 40. The microprocessorin the pressure controller 22 also receives signals from the dataacquisition board 40 to regulate the opening and closing of the valve topressurize or depressurize the chambers as needed. Apparatus 10 alsocomprises a power source and it is integrated in a system with a dataacquisition board 40 which communicates data to a computer equipped withcontrol software for human to machine interface. The system can alsohave capabilities to provide output as web based, digital storage, printout and the like.

FIG. 8 also shows that the apparatus also comprises a flow controller 24comprising a microprocessor, a laminar flow sensor, a valve, and apressure sensor. The microprocessor in the flow controller 24 regulatesopening and closing of the valve to regulate airflow into second chamber18, and integrates and analyzes signals from chamber 18 and communicatessignals to and from the data acquisition board 40 for integration andresponse. The data acquisition board 40 can receive and send data asanalog signals.

FIG. 8 depicts how the closed-loop resistance test system iselectronically integrated. In one embodiment, and during operation, theapparatus can measure pressure across an inhaler and rate of airflowthrough that inhaler simultaneously.

In embodiments herewith, a method for measuring the resistance of aninhaler to air flow due to the geometries of the air conduits of theinhaler is disclosed; wherein the method comprises installing oradapting an inhaler in a dosing configuration into the apparatus;creating an air pathway between the inhaler and a first device and asecond device of the apparatus by making a seal to ambient environmentand forming a first chamber and a second chamber; actuating a vacuumpump connected to the apparatus so that pressure in the first chamber ismaintained at one atmosphere; measuring the pressure differential acrossthe first chamber and second chamber when the flow rate of a gas intothe chamber is set at varying predetermined values to obtain data; andanalyzing the data obtained and determining the resistance to airflow ofthe inhaler. In one embodiment, once the linear range of the curve forpressure drop versus flow rate is determined based on the Bernoulliprinciple for a particular inhaler type, the resistance to airflow ofother inhalers having similar geometric air conduits can be measured atpredetermined values of within the linear range of the curve.

In one embodiment, the predetermined values of flow rates setting varyfor the inhaler type and can be assessed for each inhaler after multipletests to attain a linear range for pressure versus flow rate. Theapparatus disclosed herein can be used at various flow rates settingdepending on the inhaler internal air conduits. In one embodiment, flowrate settings can be greater than 0.1 L/min. In another embodiment, theflow rate settings can range from about 3 L/min to about 60 L/min. Inanother embodiment, the apparatus can be used a varying pressure dropsdepending on the inhaler design. Predetermined pressure drop valuesettings can be greater than 0.1 kPa^(1/2).

While the apparatus describe above and in the examples below performmeasurements through microprocessor controlled systems, in alternateembodiments, the system can operate with other types of control systemssuch as mechanical.

EXAMPLE 1

Measuring the resistance of dry powder inhalers: Three different drypowder inhaler designs manufactured by MannKind Corporation were used inthese experiments, including the MEDTONE® inhaler and two other designsdisclosed in U.S. patent applications Ser. Nos. 12/413,405 (US2009/0241949); 12/484,129 (US 2009/0308391) and 12/484,125 (US2009/0308390), which disclosures are incorporated herein by reference asthey pertain.

To measure the resistance of the each inhaler, the inhaler in the dosingconfiguration was placed or mounted to the first chamber. The dosingconfiguration forms an air pathway through the inhaler air conduits andthrough the cartridge in the inhaler. The second device is moved so thatit engages the first device. The system is actuated and the vacuum pumpevacuates the first chamber so the pressure is maintained atapproximately one atmosphere (1 atm) at all times. Other pressuresettings can be applied depending on the inhaler to be tested. Airflowis then provided at different settings and multiple times so the systemcan measure the pressure across the inhaler and airflow rate through theinhaler. The data is then analyzed and graphed for the desiredparameters.

Since different inhaler designs exhibit different resistance values dueto the different geometries of their air pathways, multiple experimentswere conducted to determine the ideal interval for pressure settings touse with each particular design. Based on the Bernoulli principle, andonly where linearity exists between the square root of pressure and flowrate, the linearity intervals were predetermined for the three inhalersused after multiple tests so that the appropriate settings could be usedwith other batches of the same inhaler design, having the same geometricconfigurations of their air pathways. FIGS. 9, 10 and 11 are graphs ofmeasurements of pressure and flow rates made, respectively, for MEDTONE®(FIG. 2, 20), and two other inhaler prototypes. The numbers are averagesof multiple measurements from multiple inhalers. FIG. 9 depicts a graphof the measurements of flow rate in liters/minute (L/min) in the x-axisversus square root of pressure differential (kPa^(1/2)) for MEDTONE®,showing that the interval for measuring the resistance of this inhalerprototype falls at a flow rate of about 30 L/min to about 40 L/min atpressure differentials of about 3.2 to about 4 square root of pressuredrop (kPa^(1/2)). FIG. 10 depicts a graph of the measurements made witha second inhaler prototype (GEN 2A), which shows that for this design,the predetermined interval which reflects linearity of pressure and flowrate was for flow rates from about 10 L/min to about 28 L/min and forpressure differential of from about 1 kPa^(1/2) to about 2.3 kPa^(1/2).FIG. 11 shows a graph for the third inhaler prototype (GEN 2B), in whichthe interval reflecting linearity was determined to be between about 1kPa^(1/2) and 2.3 kPa^(1/2), similarly as the GEN 2A inhaler.

EXAMPLE 2

Resistance test measurements were made with settings within thepredetermined Bernoulli interval for three different inhaler designs fordifferent batches of the respective inhalers using the apparatus andsystem described herewith. All three tests were conducted at flow ratesand pressure drops established by their respective intervals or whereinlinearity was attained for the inhaler type tested. Three predeterminedsettings were used and measurements were made multiple times for eachinhaler as follows. The inhaler is installed in the holder, the vacuumis turned on and the apparatus is closed to ambient air. The system canoperate automatically as follows with reference to FIG. 7:

System start-up and stabilization: The pressure controller valve isopened to achieve the first set point, i.e., pressure differentialacross the inhaler, which is equal to absolute pressure in Chamber A(FIG. 7) (i.e. first chamber 12; FIGS. 1-6) minus absolute pressure inChamber B (i.e. second chamber 18; FIGS. 1-6). The pressure in Chamber Ais then maintained at 1 atmosphere and the system is allowed tostabilize for approximately 10 seconds. The system then measurespressure and flow rate of an inhaler at three different settings (Testconditions):

Test condition 1: The pressure drop and flow rate through the inhaler ismeasured 10 times during which the pressure differential between ChamberA and Chamber B is within 5% of the set point, which set point isdetermined by the inhaler design. Each time the pressure controllerrecords a pressure drop measurement, the flow controller records a flowrate measurement so that 10 pressure and 10 flow rate values aremeasured.

Test condition 2: The pressure is adjusted by the pressure controllervalve to achieve the second set point pressure drop across the inhalerand the Chamber A pressure is maintained at approximately 1 atmosphereuntil the system is stabilized. Pressure drop and flow rate through theinhaler are measured again 10 times during which the pressuredifferential is within 5% of the set point. Again, each time thepressure controller records a pressure drop measurement, the flowcontroller also records a flow rate measurement and thus 10 pressure andcorresponding flow rate values are obtained.

Test condition 3: The pressure controller valve is once again adjustedto achieve the third set point pressure drop across the inhaler. Again,Chamber A is maintained at approximately one atmosphere and the systemis allowed to stabilize. The pressure drop between the chambers and flowrate through the inhaler are measured 10 times to obtain 10 morepressure and flow rate measurements.

Calculations: The average of the pressure drop values and correspondingflow rate conditions from each of the test conditions is determined andplotted as the square root of pressure drop versus flow rate for allthree conditions. A linear regression of the data is performed to forcethe curve through the origin and the slope of the linear regression plotis equal to the resistance value of the inhaler tested. The coefficientof determination of this linear regression is also calculated to confirmthat no irregularities occurred during testing. The R² value must exceed0.990 for the inhalers tested.

FIGS. 12, 13 and 14 are graphs showing data of measurements made fromthe three different inhalers using the apparatus described herewith.FIG. 12 depicts data exemplary of a MEDTONE® inhaler showing thefunction and the coefficient of determination quantifying the linearregression. As seen in the graph, the resultant value for this inhalerwas determined as 0.1087 (√kPa)/L per minute. FIG. 13 depicts dataexemplary of a second (GEN 2A) inhaler showing the function and thecoefficient of determination quantifying the linear regression. As seenin the graph, the resultant value for this inhaler was determined as0.0858 (√kPa)/L per minute. FIG. 14 depicts data exemplary of a third(GEN 2B) inhaler showing the function and the coefficient ofdetermination quantifying the linear regression. As seen in the graph,the resultant value for this inhaler was determined as 0.093 (√kPa)/Lper minute.

The preceding disclosures are illustrative embodiments. It should beappreciated by those of skill in the art that the techniques disclosedherein elucidate representative techniques that function well in thepractice of the present disclosure. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments that are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.Recitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is deemedto contain the group as modified thus fulfilling the written descriptionof all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Ofcourse, variations on these described embodiments will become apparentto those of ordinary skill in the art upon reading the foregoingdescription. The inventor expects skilled artisans to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. All references cited in thisspecification, and their references, are incorporated by referenceherein in their entirety where appropriate for teachings of additionalor alternative details, features, and/or technical background.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

We claim:
 1. An apparatus, comprising: a first chamber configured tomount an inhaler and having a first valve; a second chamber having asecond valve; wherein said second chamber is movable and sealablyattachable to said first chamber; a pressure controller connected tosaid first chamber and comprising a pressure sensor configured tocommunicate a first set of signals to at least one microprocessor; and aflow controller including a flow sensor and a pressure sensor connectedto said second chamber configured to communicate a second set of signalsto the at least one microprocessor, wherein the at least onemicroprocessor is configured to control opening and closing the firstvalve and the second valve.
 2. The apparatus of claim 1, furthercomprising an additional microprocessor configured to read an outputfrom corresponding sensors' output and implement an algorithm to analyzethe signals and calculate resistance values of the inhaler.
 3. Theapparatus of claim 1, wherein said first chamber is configured to holdan inhaler in place and create a seal between the first chamber and thesecond chamber.
 4. The apparatus of claim 1, wherein the first set ofsignals and the second set of signals generate data that when analyzedare correlated to resistance to airflow of the device.
 5. The apparatusof claim 1, wherein the apparatus is configured to measure resistance toairflow of the inhaler when the first chamber and the second chamberform a closed loop devoid of ambient air.
 6. A method for measuring theresistance to airflow of an inhaler, comprising: attaching a secondchamber to said a chamber to enclose said inhaler and form an airpathway from the first chamber, through the inhaler air, and into thesecond chamber; obtaining a controlled constant pressure environment inthe second chamber; and simultaneously measuring pressure differentialacross the inhaler and flow rate through the inhaler to generatepressure and flow rate measurements.
 7. The method of claim 6, whereinthe controlled constant pressure environment is maintained by aclosed-loop algorithm.
 8. The method of claim 6, wherein pressure andflow rate measurements from various test set points of the inhaler areanalyzed with an algorithm to generate a resistance value for theinhaler.
 9. The method of claim 8, wherein the resistance value for theinhaler is determined using pressure differential measurements.
 10. Themethod of claim 8, wherein the pressure and flow rate measurements aremade at predetermined pressure drop settings for the inhaler.
 11. Amethod for determining resistance to airflow of an inhaler, comprising:determining the range of measurements at which a square root of thepressure differential versus flow rate curve for an inhaler type islinear to yield predetermined value settings; obtaining pressuredifferential and flow rate measurements at various predetermined valuesettings within the linear range for a second inhaler and determiningthe slope of the curve to obtain a resistance value for the inhaler. 12.The method of claim 11, wherein the predetermined flow rate settings aregreater than 0.1 L/min.
 13. The method of claim 11, wherein at leastthree predetermined value settings are used to measure pressuredifferential and flow rate and determine the resistance value of theinhaler.
 14. The method of claim 11, further comprising the step ofmeasuring flow rate and determining the square root of the pressuredifferential across an inhaler in an apparatus comprising a firstchamber and a second chamber; wherein said inhaler is installed in thesecond chamber.
 15. The method of claim 13, wherein a linear regressionof pressure and flow data collected at the at least three predeterminedvalue settings results in a coefficient of determination greater than0.9.